U.S. patent number 10,974,504 [Application Number 16/720,940] was granted by the patent office on 2021-04-13 for liquid ejection head and control method of liquid ejection head.
This patent grant is currently assigned to Canon Kabushiki Kaisha. The grantee listed for this patent is CANON KABUSHIKI KAISHA. Invention is credited to Ryo Kasai, Yoshiyuki Nakagawa, Toru Nakakubo, Kazuhiro Yamada, Takuro Yamazaki.
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United States Patent |
10,974,504 |
Yamazaki , et al. |
April 13, 2021 |
Liquid ejection head and control method of liquid ejection head
Abstract
A liquid ejection head can stably eject a liquid from an
ejection port by mitigating thickening of the liquid by evaporation
from the ejection port. The liquid ejection head has a support
substrate; a liquid chamber arranged on the support substrate and
provided with an energy generating element for generating energy
necessary for ejection of a liquid and an ejection port from which
the liquid is ejected; and a circulation flow path of the liquid
that passes through the liquid chamber. The liquid ejection head
further has a first circulating element that forms a first
circulatory flow in the circulation flow path; and a second
circulating element that forms a second circulatory flow inside the
liquid chamber and a driving frequency of the first circulating
element is lower than a driving frequency of the second circulating
element.
Inventors: |
Yamazaki; Takuro (Inagi,
JP), Nakagawa; Yoshiyuki (Kawasaki, JP),
Nakakubo; Toru (Kawasaki, JP), Yamada; Kazuhiro
(Yokohama, JP), Kasai; Ryo (Tokyo, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
CANON KABUSHIKI KAISHA |
Tokyo |
N/A |
JP |
|
|
Assignee: |
Canon Kabushiki Kaisha (Tokyo,
JP)
|
Family
ID: |
1000005483463 |
Appl.
No.: |
16/720,940 |
Filed: |
December 19, 2019 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
|
US 20200198335 A1 |
Jun 25, 2020 |
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Foreign Application Priority Data
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|
|
|
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Dec 25, 2018 [JP] |
|
|
JP2018-241290 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B41J
2/18 (20130101); B41J 2/04573 (20130101); B41J
2/14145 (20130101); B41J 2/0458 (20130101) |
Current International
Class: |
B41J
2/18 (20060101); B41J 2/14 (20060101); B41J
2/045 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
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2017-177437 |
|
Oct 2017 |
|
JP |
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2011/146069 |
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Nov 2011 |
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WO |
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2013/130039 |
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Sep 2013 |
|
WO |
|
Primary Examiner: Tran; Huan H
Attorney, Agent or Firm: Venable LLP
Claims
What is claimed is:
1. A liquid ejection head comprising: a support substrate; a liquid
chamber arranged on the support substrate and provided with an
energy generating element for generating energy necessary for
ejection of a liquid and an ejection port from which the liquid is
ejected; a circulation flow path of the liquid that passes through
the liquid chamber; a first circulating element that forms a first
circulatory flow in the circulation flow path; and a second
circulating element that forms a second circulatory flow inside the
liquid chamber, wherein a driving frequency of the first
circulating element is lower than a driving frequency of the second
circulating element.
2. The liquid ejection head according to claim 1, wherein the first
circulating element is arranged outside the liquid chamber, and the
second circulating element is arranged inside the liquid
chamber.
3. The liquid ejection head according to claim 1, wherein the first
circulatory flow is a flow that collects the liquid not ejected
from the ejection port from the liquid chamber as well as guides
the liquid to the liquid chamber, and the second circulatory flow
is a flow that circulates inside the liquid chamber.
4. The liquid ejection head according to claim 1, wherein the
second circulatory flow includes a flow component that advances
from the inside of the liquid chamber toward the ejection port.
5. The liquid ejection head according to claim 1, wherein the first
circulating element is a heating element or an electrode pair, and
the second circulating element is an electrode pair.
6. The liquid ejection head according to claim 5, wherein the first
circulating element is a heating element, and a size of the heating
element is larger than a size of the energy generating element.
7. The liquid ejection head according to claim 5, wherein in a case
where the first circulating element is an electrode pair, the first
circulatory flow is an AC electroosmotic flow or an AC
electrothermal flow and the second circulatory flow is an AC
electroosmotic flow or an AC electrothermal flow.
8. The liquid ejection head according to claim 7, wherein a first
electrode and a second electrode configuring the electrode pair of
the second circulating element are arranged so as to be symmetrical
with respect to the ejection port as a reference.
9. The liquid ejection head according to claim 8, wherein a
rotation direction of a first vortex flow formed in the vicinity of
the first electrode is opposite to a rotation direction of a second
vortex flow formed in the vicinity of the second electrode.
10. The liquid ejection head according to claim 1, wherein at least
one of the first circulating element and the second circulating
element is driven by interlocking with timing at which the energy
generating element is driven.
11. The liquid ejection head according to claim 10, wherein at
least one of the first circulating element and the second
circulating element is driven by avoiding a period during which the
energy generating element is driven and a predetermined period
before and after being driven.
12. The liquid ejection head according to claim 1, wherein both the
first circulating element and the second circulating element are
provided on the support substrate.
13. The liquid ejection head according to claim 1, wherein the
ejection port is formed in a member that the support substrate
supports, and the first circulating element and the second
circulating element are provided at positions different in height
in a direction perpendicular to a bonding face of the support
substrate and the member.
14. The liquid ejection head according to claim 13, wherein the
first circulating element is provided in the support substrate, and
the second circulating element is provided in the member.
15. The liquid ejection head according to claim 14, wherein at
least a part of the second circulating element is arranged inside
the ejection port.
16. The liquid ejection head according to claim 1, wherein each of
an end portion on an upstream side in the circulation flow path and
an end portion on a downstream side in the circulation flow path
communicates with an identical flow path.
17. A control method of a liquid ejection head having: a support
substrate; a liquid chamber arranged on the support substrate and
provided with an energy generating element for generating energy
necessary for ejection of a liquid and an ejection port from which
the liquid is ejected; and a circulation flow path of the liquid
that passes through the liquid chamber, the control method
comprising: a first step of forming a first circulatory flow in the
circulation flow path by a first circulating element; and a second
step of forming a second circulatory flow inside the liquid chamber
by a second circulating element, wherein a driving frequency of the
first circulating element is lower than a driving frequency of the
second circulating element.
18. The control method according to claim 17, wherein the first
step and the second step are performed at identical timing.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a liquid ejection head and a
control method of a liquid ejection head.
Description of the Related Art
In an ink jet printer, a liquid ejection head (also referred to as
print head) for ejecting a liquid, such as ink, is mounted. In the
liquid ejection head, as a result of a volatile component in a
liquid evaporating from an ejection port from which a liquid is
ejected, there is a case where the liquid in the vicinity of the
ejection port thickens. By thickening of the liquid, there is a
case where the ejection velocity of liquid droplets to be ejected
changes or the landing accuracy is affected. In particular, in a
case where the printer rest time after performing ejection is long,
thickening of the liquid advances and the solid component of the
liquid solidifies in the vicinity of the ejection port. As a result
of this, by the solid component, the liquid resistance of the
liquid increases and there is a case where defective ejection
occurs.
As one of the measures against the thickening phenomenon of the
liquid such as this, a method is known in which a liquid that has
not thickened yet (so-called fresh liquid) is caused to flow
through a liquid chamber, and in addition thereto, the ejection
port. As a method of causing a liquid to flow, there is known a
method of causing a liquid within the head to circulate by a
differential pressure method. International Publication No. WO
2011/146069 has disclosed a method in which a pull-in flow of a
liquid from the side of the flow path whose flow resistance is low
is used at the time of refill after heating and bubble generation
by an auxiliary resistor arranged at an asymmetrical position of
the within-flow path flow resistance. International Publication No.
WO 2013/130039 has disclosed a method that uses a micro pump
causing an AC electroosmotic flow (ACEOF) to occur.
SUMMARY OF THE INVENTION
However, by the method described in International Publication No.
WO 2011/146069, the velocity of the pull-in flow depends on the
flow path resistance at the time of refill, and therefore, in a
case where a liquid having a high viscosity, such as an ink whose
pigment concentration is high, is used or in a case where a flow
path whose width or height is small is adopted, there is a
possibility that sufficient flow velocity is not obtained. Because
of that, it is not possible to cause a liquid sufficiently fresh
for sending out the liquid concentrated within the ejection port to
flow into the liquid chamber, and therefore, the concentrated
liquid is likely to stagnate within the ejection port.
According to the method described in International Publication No.
WO 2013/130039, it is possible to cause a fresh ink to flow into
the liquid chamber. However, an element that plays a role of a pump
does not exist in the flow path on the downstream side of the
ejection port, and therefore, the effect of causing a liquid within
the ejection port to flow out is faint. Because of this, the
concentrated liquid is likely to stagnate within the ejection port.
As described above, these patent documents have such a problem that
the liquid within the ejection port is likely to thicken due to
evaporation of the liquid from the ejection port.
Consequently, in view of the above-described problem, an object of
the present invention is to mitigate thickening of a liquid due to
evaporation from the ejection port and make it possible to stably
eject a liquid from the ejection port.
One embodiment of the present invention is a liquid ejection head
including: a support substrate; a liquid chamber arranged on the
support substrate and provided with an energy generating element
for generating energy necessary for ejection of a liquid and an
ejection port from which the liquid is ejected; and a circulation
flow path of the liquid that passes through the liquid chamber, and
the liquid ejection head further includes: a first circulating
element that forms a first circulatory flow in the circulation flow
path; and a second circulating element that forms a second
circulatory flow inside the liquid chamber and a driving frequency
of the first circulating element is lower than a driving frequency
of the second circulating element.
Further features of the present invention will become apparent from
the following description of exemplary embodiments with reference
to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A to FIG. 1D are each a schematic diagram of a liquid
ejection head according to a first embodiment;
FIG. 2A to FIG. 2C are each a schematic diagram for explaining a
mechanism of occurrence of a liquid flow path circulatory flow;
FIG. 3A to FIG. 3D are each a schematic diagram for explaining a
mechanism of occurrence of a flow velocity distribution that occurs
by an electroosmotic flow;
FIG. 4A to FIG. 4C are each a diagram showing each drive signal of
a first circulating element and a second circulating element;
FIG. 5A to FIG. 5C are each a diagram showing each drive timing of
an energy generating element, the first circulating element, and
the second circulating element;
FIG. 6A to FIG. 6D are each a schematic diagram of a liquid
ejection head according to a second embodiment;
FIG. 7A and FIG. 7B are each a schematic diagram of a liquid
ejection head according to a third embodiment;
FIG. 8A to FIG. 8C are each a schematic diagram for explaining a
mechanism of occurrence of a flow velocity distribution that occurs
by an AC electrothermal flow;
FIG. 9A to FIG. 9C are each a schematic diagram of a liquid
ejection head according to a fourth embodiment;
FIG. 10A to FIG. 10C are each a schematic diagram of a liquid
ejection head according to a fifth embodiment; and
FIG. 11A and FIG. 11B are each a schematic diagram of a liquid
ejection head according to a sixth embodiment.
DESCRIPTION OF THE EMBODIMENTS
In the following, with reference to the drawings, a liquid ejection
head according to embodiments of the present invention is
explained. In each of the following embodiments, an ink jet print
head that ejects ink and an ink jet printing apparatus are taken to
be the target, but the present invention is not limited to this. It
is possible to apply the present invention to a printer, a copy
machine, a facsimile machine having a communication system, a
device, such as a word processor having a printer unit, and
further, an industrial printing apparatus that compositely combines
various processing apparatuses. For example, it is possible to use
the present invention for the purpose of biochip manufacturing,
electronic circuit printing, and the like.
The embodiments described in the following are preferred specific
examples of the present invention and a variety of technically
favorable restrictions are imposed thereon. However, as long as the
thought of the present invention is observed, the present invention
is not limited to the embodiments described below.
First Embodiment
<About Structure of Liquid Ejection Head>
FIG. 1A is a perspective diagram of a printing element substrate 1,
which is a part of a liquid ejection head according to a first
embodiment of the present invention. FIG. 1B is a schematic diagram
showing a liquid movement direction on a plane obtained by
truncating the printing element substrate 1 in a plane parallel to
a bonding face of a support substrate 10 and an ejection port
forming member 15 shown in FIG. 1A. FIG. 1C is a schematic diagram
showing a liquid movement direction on a section along an IC-IC
line in FIG. 1B. FIG. 1D is a schematic diagram showing a liquid
movement direction on a section along an ID-ID line in FIG. 1B.
The printing element substrate 1 has the support substrate 10 and
the ejection port forming member 15. The ejection port forming
member 15 is bonded to the support substrate 10. The support
substrate 10 is provided with an energy generating element 11 for
generating energy necessary for ejection of ink. The energy
generating element 11 is provided for each liquid chamber (also
referred to as pressure chamber) 21. In the ejection port forming
member 15, a plurality of ejection ports 12 is arranged. The
plurality of the ejection ports 12 is arrayed in one row and forms
an ejection port row 20. The printing element substrate 1 of the
present embodiment has two rows of the ejection port row 20, but
the number of ejection port rows 20 is not limited to this and an
arbitrary one value may be adopted.
As shown in FIG. 1A, the direction in which the ejection ports are
arrayed is taken to be a Y-axis direction, the direction in which
ink is ejected from the ejection port is taken to be a Z-axis
direction, and the direction perpendicular to the Y-axis direction
and the Z-axis direction is taken to be an X-axis direction. This
coordinate axes are also used in common in subsequent
explanation.
As shown in FIG. 1B and FIG. 1C, by a space between the ejection
port forming member 15 and the support substrate 10 being
partitioned by a flow path forming member 22, a liquid flow path 13
for each ejection port 12 is formed. The liquid flow path 13 is a
part of the flow path (referred to as circulation flow path)
through which ink circulates and in the liquid flow path 13, a
plurality of the liquid chambers 21 comprising the energy
generating element 11 and the ejection port 12 corresponding to
each liquid flow path 13 is formed on the support substrate 10.
In the space between the ejection port forming member 15 and the
support substrate 10, the liquid chamber 21 is formed by the space
being partitioned by the flow path forming member 22. The liquid
chamber 21 is a space partitioned by the support substrate 10, the
ejection port forming member 15, and the flow path forming member
22, and provided on the way of the liquid flow path 13, and has a
dimension equal to or more than that of the liquid flow path 13 in
the Y-axis direction. In each of the plurality of the liquid
chambers 21 on the printing element substrate 1, the energy
generating element 11 and second circulating elements 17 and 17',
to be described later, are arranged.
The ejection port 12 faces the energy generating element 11 in the
direction perpendicular to the bonding face of the support
substrate 10 and the ejection port forming member 15. The liquid
flow path 13 is connected, at the end portion on the upstream side,
to a first liquid supply flow path 14 formed between the ejection
port forming member 15 and the support substrate 10 and at the end
portion on the downstream side, connected to a second liquid supply
flow path 14' formed between the ejection port forming member 15
and the support substrate 10. Consequently, the first liquid supply
flow path 14, the liquid flow path 13, the liquid chamber 21, and
the second liquid supply flow path 14' form an independent flow
path for each ejection port 12. The first liquid supply flow path
14 and the second liquid supply flow path 14' extend in parallel to
the ejection port row 20 with the ejection port row 20 being
sandwiched in between and connected to an ink supply tank, not
shown schematically.
Ink is supplied from the first liquid supply flow path 14 to the
liquid chamber 21 through the liquid flow path 13. The ink supplied
to the liquid chamber 21 is heated by the energy generating element
11 and ejected from the ejection port 12 by a force of air bubbles
generated by heating. The ink that is not ejected from the ejection
port 12 is guided from the liquid chamber 21 to the second liquid
supply flow path 14' through the liquid flow path 13. The ink
guided to the second liquid supply flow path 14' is ejected from
another ejection port, or the ink not ejected from any ejection
port is finally returned to an ink supply tank, not shown
schematically.
In the liquid flow path 13, a first circulating element 16 is
provided on the support substrate and at the same time, within the
liquid chamber 21, the second circulating elements 17 and 17' are
provided. The first circulating element 16 is configured by a
heating element and the like. The first circulating element 16 may
have the same configuration as that of the energy generating
element 11 or may have a different configuration. The dimension of
a first electrode and that of a second electrode are the same, both
included in an electrode pair of the second circulating elements 17
and 17'. A pair of these electrodes is formed at a position whose
height is different from that of the energy generating element 11
on the support substrate so that the electrodes are symmetrical
with respect to the energy generating element 11 as a reference
(specifically, in the form in which the electrodes sandwich the
energy generating element 11). Each electrode of the electrode pair
of the second circulating elements 17 and 17' is connected to one
end of an alternating-current power source AC by a wire, not shown
schematically, via a contact hole 23. Here, it is assumed that the
electrode forming the second circulating element 17 is connected to
the + terminal of the alternating-current power source AC and on
the other hand, the electrode forming the second circulating
element 17' is connected to the - terminal of the
alternating-current power source AC. However, the electrode forming
the second circulating element 17 may be connected to the -
terminal of the alternating-current power source AC and the
electrode forming the second circulating element 17' may be
connected to the + terminal of the alternating-current power source
AC.
<About Liquid Flow Path Circulatory Flow 18 that Occurs by First
Circulating Element 16>
To the heating element of the first circulating element 16, a
heating pulse current is applied. As a result of that, as shown in
FIG. 1B and FIG. 1C, a liquid flow path circulatory flow 18 that
advances from one end of the liquid flow path 13 toward the other
end occurs. The liquid flow path circulatory flow 18 is a flow that
collects the liquid not ejected from the ejection port 12 from the
liquid chamber 21 as well as guiding the liquid to be ejected to
the liquid chamber 21. The reason the liquid flow path circulatory
flow 18 occurs is explained by using FIG. 2A to FIG. 2C. FIG. 2A to
FIG. 2C are each a schematic diagram for explaining the mechanism
of occurrence of the liquid flow path circulatory flow 18 at the
section position shown in FIG. 1C.
FIG. 2A is a diagram showing the way ink is heated by the heating
element of the first circulating element 16 and an air bubble 220
generated by film boiling grows. The first circulating element 16
is arranged at a position whose distances to the positions of both
end portions of the liquid flow path 13 are different, a so-called
within-flow path asymmetrical position. One end portion of the
liquid flow path 13 is connected to the first liquid supply flow
path 14 and the other end portion of the liquid flow path 13 is
connected to the second liquid supply flow path 14'. In a case
where the flow resistance in the first liquid supply flow path 14
is sufficiently high compared to the liquid flow path 13, the flow
resistance in the liquid flow path 13 in the range from the first
circulating element 16 to the first liquid supply flow path 14
mainly depends on the distance between the first circulating
element 16 and the first liquid supply flow path 14. Similarly, in
a case where the flow resistance in the second liquid supply flow
path 14' is sufficiently high compared to the liquid flow path 13,
the flow resistance in the liquid flow path 13 in the range from
the first circulating element 16 to the second liquid supply flow
path 14' mainly depends on the distance between the first
circulating element 16 and the second liquid supply flow path
14'.
In a case in FIG. 2A, the flow resistance from the first
circulating element 16 to the first liquid supply flow path 14 on
the left side in FIG. 2A is lower than the flow resistance from the
first circulating element 16 to the second liquid supply flow path
14' on the right side in FIG. 2A. Consequently, the air bubble 220
due to film boiling is formed so as to inflate toward the left side
whose flow resistance is low. A liquid movement 210 by bubble
generation indicates that the air bubble 220 grows more on the left
side in FIG. 2A whose flow resistance is low compared to the right
side in FIG. 2A.
FIG. 2B shows a shrinkage process of the air bubble 220. In the
shrinkage process of the air bubble, as shown by an arrow 211, more
ink is refilled from the liquid flow path 13 on the left side in
FIG. 2B whose flow resistance is low than from the liquid flow path
13 on the right side in FIG. 2B whose flow resistance is high. As a
result of this, as shown in FIG. 2C, the bubble disappearance
position of the air bubble 220 shifts from the position on the
first circulating element 16 toward the right side in FIG. 2C whose
flow resistance is high and from a macroscopic viewpoint, a flow
that advances in one direction from one end of the liquid flow path
13 toward the other end, that is, the liquid flow path circulatory
flow 18 occurs. This liquid flow path circulatory flow 18
attenuates as the air bubble 220 disappears and stops after a
predetermined time elapses.
In order to cause the liquid flow path circulatory flow 18 to occur
steadily for a certain time, bubble generation and refill by the
first circulating element 16 described previously are repeated. By
the liquid flow path circulatory flow 18 that occurs by the first
circulating element 16 provided in the liquid flow path 13, fresh
ink flows from the first liquid supply flow path 14 into the liquid
chamber 21 through the liquid flow path 13. In a case where the
energy generating element 11 is operating, part of the ink having
flowed into the liquid chamber 21 is ejected from the ejection port
12. The ink that is not ejected from the ejection port 12 flows out
to the second liquid supply flow path 14' through the liquid flow
path 13.
Also in a case where the energy generating element 11 is not
operating, the liquid flow path circulatory flow 18 occurs by
applying a heating pulse current to the heating element of the
first circulating element 16, and therefore, the ink flows through
the liquid flow path 13 from the side of the first liquid supply
flow path 14 toward the side of the second liquid supply flow path
14'. Consequently, even in a case where the ink concentrates within
the liquid chamber 21, it is possible to suppress stagnation of the
concentrated ink within the liquid chamber 21.
The driving cycle of the first circulating element 16 configured by
the heating element and the like is not limited in particular as
long as it is possible to attain discharge of the concentrated ink
within the liquid chamber 21, but preferably, it is possible for
the first circulating element 16 to drive at about 100 Hz to 10
kHz. However, in a case where the drive frequency representing the
number of driving times of the first circulating element 16 per
unit time is high, there is a possibility that the rise of the ink
temperature within the liquid flow path 13 due to heating becomes
problematic. Consequently, it is preferable to set an upper limit
value of the drive frequency in accordance with the allowable
amount of temperature rise.
<About Flow Velocity Distribution and Liquid Chamber Circulatory
Flow 19 that Occur by Second Circulating Elements 17 and
17'>
To the electrodes configuring the second circulating elements 17
and 17', an alternating-current voltage is applied. As a result of
that, as indicated by an arrow in FIG. 1D, a flow velocity
distribution occurs within the liquid chamber 21, in which the flow
velocity is high on the surface of the support substrate 10 and the
flow velocity gradually approaches zero as the ejection port
forming member 15 becomes nearer. The reason this flow velocity
distribution occurs is explained by using FIG. 3A to FIG. 3D.
The two electrodes configuring the second circulating elements 17
and 17' are taken to be a first electrode 310 and a second
electrode 311, respectively. The first electrode 310 and the second
electrode 311 have the same dimension. As shown in FIG. 3A, an
electric double layer occurs in the first electrode 310 and the
second electrode 311, respectively. To explain in detail, a
positive voltage (+V) is applied to the first electrode 310 and the
ink in contact with the first electrode 310 is charged negatively,
and thus, an electric double layer configured by a lower layer
charged positively and an upper layer charged negatively is formed.
Similarly, a negative voltage (-V) is applied to the second
electrode 311 and the ink in contact with the second electrode 311
is charged positively, and thus, an electric double layer
configured by a lower layer charged negatively and an upper layer
charged positively is formed.
By the ink being charged as described previously, in the ink, an
electric field E in the shape of a semicircle is formed, which
extends from the first electrode 310 toward the second electrode
311. This electric field is symmetrical with respect to the
intermediate line between the first electrode 310 and the second
electrode 311. On the surface of the first electrode 310, an
electric field component E1 parallel to the surface of the first
electrode 310 is generated and similarly, on the surface of the
second electrode 311, the electric field component E1 parallel to
the surface of the second electrode 311 is generated. The electric
field component E1 exerts the Coulomb force on charges induced on
the first electrode 310 and charges induced on the second electrode
311. The electric field component E1 faces in the leftward
direction in FIG. 3A at a position in the vicinity of a gap
(referred to as inter-electrode gap) between the first electrode
310 and the second electrode 311. The positive charge receives a
force whose direction is the same as that of the electric field,
and therefore, as shown in FIG. 3B, a rotation vortex F1 occurs,
which causes the ink in the vicinity of the second electrode 311 to
flow in the leftward direction in FIG. 3B. On the contrary, the
negative charge receives a force whose direction is opposite to
that of the electric field, and therefore, a rotation vortex F2
occurs, which causes the ink in the vicinity of the first electrode
310 to flow in the rightward direction in FIG. 3B. Due to the
rotation vortex F1 and the rotation vortex F2, the ink flows in the
direction away from the inter-electrode gap, and therefore, an ink
flow F3 that replenishes ink occurs in the inter-electrode gap.
Further, at each electrode, at the end portion apart from the
inter-electrode gap, the direction of the electric field is
opposite to that at the end portion near to the inter-electrode
gap, and therefore, a rotation vortex F4 occurs, whose rotation
direction is opposite to that of the rotation vortex that occurs at
the end portion near to the inter-electrode gap. However, compared
to the end portion near to the inter-electrode gap, the electric
field component E1 at the end portion apart from the
inter-electrode gap is weak, and therefore, the Coulomb force
exerted on the ink is small. As a result of this, a stir flow that
advances from the inter-electrode gap toward the first electrode
310 and advances in the direction away from the inter-electrode gap
on the first electrode 310 and a stir flow that advances from the
inter-electrode gap toward the second electrode 311 and advances in
the direction away from the inter-electrode gap on the second
electrode 311 are formed. As shown in FIG. 3B, these two stir flows
are bilaterally symmetrical.
In FIG. 3A and FIG. 3B, the case is explained where the first
electrode 310 and the second electrode 311 have the same dimension.
In contrast to this, in a case where the first electrode 310 and
the second electrode 311 have different dimensions (specifically,
different widths), as shown in FIG. 3C and FIG. 3D, the electric
field distribution is different between the first electrode 310 and
the second electrode 311. By the electric field distribution such
as this, at the position in the vicinity of the second electrode
311 and at which the potential is high, a rotation vortex F5 whose
flow velocity is high and whose diameter is small is formed. On the
other hand, in the vicinity of the first electrode 310, at the
position at which the potential is low, a rotation vortex F7 whose
flow velocity is low and whose diameter is small is formed and at
the position at which the potential is high, a rotation vortex F6
whose flow velocity is low and whose diameter is large is formed.
As a result of these rotation vortexes being formed, an ink flow in
which ink is pulled into the inter-electrode gap from the second
electrode 311 and flows from the inter-electrode gap toward the
first electrode 310 occurs, that is, from a macroscopic viewpoint,
an ink flow in which ink flows from the second electrode 311 toward
the first electrode 310 occurs.
The above contents also apply similarly to a case where a positive
voltage (+V) is applied to the second electrode 311 and a negative
voltage (-V) is applied to the first electrode 310. That is, even
in a case where the polarity of the voltage to be applied is
reversed, both the sign of the charge and the orientation of the
electric filed are reversed, and therefore, the orientation of the
flow that occurs does not change. Consequently, a steady flow
occurs as a result, which advances from the second electrode 311
whose width dimension of the electrode is small toward the first
electrode 310 whose width dimension of the electrode is large. This
flow has an alternating-current frequency of 100 Hz to 100 kHz and
the flow velocity thereof is high, and called an AC electroosmotic
flow (ACEOF). Depending on the value of voltage to be added, water
electrolysis occurs, and therefore, it is desirable to set the
value of voltage to be applied in a range in which water
electrolysis does not occur.
By the steady electroosmotic flow such as this, a flow velocity
distribution occurs (see FIG. 1D), which forms two vortexes at
positions approximately symmetrical with respect to the energy
generating element 11 or the ejection port 12 as a reference. The
flow component that passes the vicinity of the ejection port 12 is
formed, and therefore, it is possible to cause the concentrated ink
in the vicinity of the ejection port 12 to flow and send the ink
into the liquid chamber. Consequently, it is easy to suppress
concentration of ink in the vicinity of the ejection port 12. The
second circulating elements 17 and 17' are connected to the
alternating-current power source AC, and therefore, the occurrence
of a bubble due to water electrolysis is suppressed compared to the
direct-current power source DC and it is possible to increase the
drive voltage.
In the present embodiment, by using the first circulating element
16 and the second circulating element 17 in combination, a
configuration is implemented in which the concentrated ink within
the ejection port 12 is pushed out efficiently and the ink can be
replaced with fresh ink.
Only by the liquid flow path circulatory flow 18 by the first
circulating element 16, the effect of pushing and causing the
concentrated ink within the ejection port 12 to flow is obtained.
However, in a case where the flow velocity is not sufficient, the
effect is limited, and therefore, there is a possibility that it is
not possible to secure sufficient ejection stability. Further, only
by the liquid chamber circulatory flow 19 by the second circulating
elements 17 and 17', the effect of sending out the concentrated ink
within the ejection port 12 into the liquid chamber 21 and diluting
the concentrated ink within the liquid chamber is obtained.
However, in a case where ejection by the energy generating element
11 is not performed for a predetermined time or more, the
concentration of the ink within the liquid chamber 21 advances, and
therefore, there is a possibility that it is no longer possible to
eject ink from the ejection port 12. As described above, in a case
where one of the first circulating element 16 and the second
circulating elements 17 and 17' is used, there is a possibility
that it is not possible to secure sufficient ejection
stability.
In order to solve this problem, in the present embodiment, by
combining the first circulating element 16 and the second
circulating elements 17 and 17', the concentrated ink within the
ejection port 12 is sent into the liquid chamber 21 by a stir flow
and at the same time, the sent concentrated ink is replaced with
fresh ink by the liquid flow path circulatory flow 18. Due to this,
even in a case where the velocity of the liquid flow path
circulatory flow 18 is lower than the conventional velocity, it is
made possible to secure ejection stability and the drive condition
of the first circulating element 16 is mitigated. Consequently, it
is possible to extend the range of alternatives relating to inks
with a variety of viscosities.
<About Driving Method of First Circulating Element 16 and Second
Circulating Elements 17 and 17'>
Next, by using FIG. 4A and FIG. 5A, a driving method of the first
circulating element 16 and the second circulating elements 17 and
17' is explained. FIG. 4A is an image diagram of a drive signal of
each of the first circulating element 16 and the second circulating
elements 17 and 17' in a case where both are driving. FIG. 5A is an
image diagram of the driving timing of the energy generating
element 11, the first circulating element 16, and the second
circulating elements 17 and 17'.
In the present embodiment, the first circulating element 16 is a
heating element. Symbol 110 in FIG. 4A indicates a pulse wave as
the drive signal of the first circulating element 16. As shown in
FIG. 4A, in order to drive the first circulating element 16, a
voltage of 24 V is applied at 1 kHz.
Further, the second circulating elements 17 and 17' are AC
electroosmotic flow generating elements. Symbol 111 in FIG. 4A
indicates a sinusoidal wave, which is the drive signal of the
second circulating elements 17 and 17'. As shown in FIG. 4A, in
order to drive the second circulating elements 17 and 17', a
sinusoidal wave alternating-current voltage that varies in a range
of .+-.2.5 V is applied at 500 Hz. The drive signal of the first
circulating element 16 and the second circulating elements 17 and
17' according to the present embodiment is not limited to each
signal waveform. It is possible to selectively set the voltage, the
frequency, and the waveform of the drive signal in a range in which
desired flow velocity is obtained for the liquid flow path
circulatory flow 18 and the liquid chamber circulatory flow 19
described previously.
As shown in FIG. 5A, the driving timing of the first circulating
element 16 is interlocked with the driving timing of the energy
generating element 11. Specifically, the first circulating element
16 drives by avoiding the period during which the energy generating
element 11 is driving and a predetermined period before and after
the drive thereof so that the first circulating element 16 is not
affected by bubble generation by the energy generating element 11,
which is a heating element, and the pressure variation by ink
refill, and thus, the liquid flow path circulatory flow 18 is
formed. On the other hand, the driving timing of the second
circulating elements 17 and 17' is not interlocked with the driving
timing of the energy generating element 11. The liquid chamber
circulatory flow 19 is formed by the second circulating elements 17
and 17' driving at all times irrespective of the presence/absence
of ejection.
In the present embodiment, by using in combination a gate array for
applying the signal shown in FIG. 4A and a gate array for applying
the signal at the timing shown in FIG. 5A, drive control for each
liquid flow path 13 described previously is implemented. However,
it may also be possible to implement this drive control by control
by software not by control by hardware. For example, it may also be
possible to make a layout in which the ink jet printing apparatus
has a CPU, a ROM, and a RAM and the drive of the first circulating
element and the second circulating element is controlled by a
program stored in the ROM being loaded onto the RAM and being
executed by the CPU.
About Effect of the Present Embodiment
By the above configuration, an ink flow that advances from one end
toward the other end within the liquid flow path 13 occurs by the
first circulating element 16 and a fresh ink flow that crosses the
liquid chamber 21 occurs. Because of this, it is possible to
suppress the ink having concentrated within the liquid chamber 21
from stagnating. Further, a flow component of the ink that advances
toward the ejection port 12 occurs within the liquid chamber 21 by
the second circulating elements 17 and 17'. Because of this, it is
possible to efficiently suppress ink concentration within the
ejection port 12. In the present embodiment, by the configuration
in which the above two are combined, it is made possible to
efficiently discharge the concentrated ink to the outside of the
liquid chamber 21 by pushing out the thickened ink within the
ejection port 12 into the liquid chamber 21 and sending fresh ink
into the liquid chamber 21. Consequently, it is possible to eject
comparatively fresh ink whose effect of reducing ink thickening
within the ejection port 12 is strong and whose degree of
thickening is low. As a result, it is made possible to reduce the
color unevenness of an image.
Second Embodiment
In the following, a printing element substrate of a liquid ejection
head according to a second embodiment is explained. In the
following explanation, differences from the first embodiment are
explained mainly. The contents of the portion whose specific
explanation is omitted are the same as those of the first
embodiment.
FIG. 6A is a schematic diagram showing the structure of the
printing element substrate 1 of the liquid ejection head according
to the second embodiment of the present invention and specifically,
FIG. 6A a diagram showing a plane obtained by truncating the
printing element substrate 1 in a plane parallel to the bonding
face of the support substrate 10 and the ejection port forming
member 15. FIG. 6B is a schematic diagram showing a liquid movement
direction on a section along a VIB-VIB line in FIG. 6A. FIG. 6C is
a schematic diagram showing a flow velocity distribution on a
section shown in FIG. 6B. FIG. 6D is a schematic diagram showing a
flow velocity distribution on a section along a VID-VID line in
FIG. 6A. FIG. 6A shows only the one ejection port 12 and the liquid
flow path 13 and the liquid supply flow paths 14 and 14'
corresponding thereto, but the configuration of the ejection port
row 20 and the liquid supply flow paths 14 and 14' is the same as
that of the first embodiment.
In the present embodiment, the liquid flow path 13 is provided with
the electrodes configuring the first circulating elements 16 and
16' and the liquid chamber 21 is provided with the electrodes
configuring the second circulating elements 17 and 17'. Both the
first circulating elements 16 and 16' and the second circulating
elements 17 and 17' are provided on the support substrate 10. One
element of the first circulating elements 16 and 16' is connected
to one end (+ terminal) of the alternating-current power source AC
and the other element is connected to the other end (- terminal) of
the alternating-current power source AC.
As for the first circulating element 16, the dimension in the
direction along the ink flow direction, that is, along the liquid
flow path 13 is greater than the dimension of the first circulating
element 16' and on the other hand, the dimension of the first
circulating element 16 in the direction perpendicular to the ink
flow direction is about the same as the dimension of the first
circulating element 16'. Consequently, the surface area of the
first circulating element 16, with which ink comes into contact, is
larger than the surface area of the first circulating element 16',
with which ink comes into contact.
A plurality of pairs of the first circulating elements 16 and 16'
is provided in the liquid flow path 13 and the first circulating
element 16 and the first circulating element 16' are provided
alternately. In the liquid flow path 13 in which the circulatory
flow is formed, it is sufficient to provide at least one pair of
the first circulating elements 16 and 16' adjacent to each other.
In the configuration illustrated in FIG. 6A to FIG. 6D, the four
pairs of the first circulating elements 16 and 16' are arranged in
the liquid flow path 13. The first circulating element 16 or each
of a plurality of the first circulating elements 16 is connected to
a first common wire and the first circulating element 16' or each
of a plurality of the first circulating elements 16' is connected
to a second common wire (not shown schematically). The pair of the
second circulating elements 17 and 17' provided within the liquid
chamber 21 is the same as that of the first embodiment.
To the electrode configuring the first circulating elements 16 and
16', an alternating-current voltage is applied. As a result of
that, as indicated by an arrow in FIG. 6C, a flow velocity
distribution occurs within the liquid flow path 13, in which the
flow velocity at the surface of the support substrate 10 is high
and the flow velocity gradually approaches zero as the ejection
port forming member 15 becomes nearer. Consequently, in each pair
of the first circulating elements 16 and 16', a steady flow occurs
that advances from the first circulating element 16' whose
dimension in the flow path direction is small toward the first
circulating element 16 whose dimension in the flow path direction
is great.
To the electrode configuring the second circulating elements 17 and
17', an alternating-current voltage is applied. As a result of
that, as shown in FIG. 6D, a flow velocity distribution occurs
within the liquid chamber 21, in which the flow velocity at the
surface of the support substrate 10 is high and the flow velocity
gradually approaches zero as the ejection port forming member 15
becomes nearer, resulting in formation of the liquid chamber
circulatory flow 19.
FIG. 4B is an image diagram of the drive signal of each circulating
element in a case where both the first circulating elements 16 and
16' and the second circulating elements 17 and 17' according to the
present embodiment are driving. In FIG. 4B, symbol 110 indicates
the sinusoidal wave as the drive signal of the first circulating
elements 16 and 16'. The first circulating elements 16 and 16' are
AC electroosmotic flow generating elements and in order to drive
the first circulating elements 16 and 16', a sinusoidal wave
alternating-current voltage that varies in a range of .+-.2.5 V is
applied at 500 Hz.
Further, in FIG. 4B, symbol 111 indicates the sinusoidal wave as
the drive signal of the second circulating elements 17 and 17'. The
second circulating elements 17 and 17' are AC electroosmotic flow
generating elements and in order to drive the second circulating
elements 17 and 17', a sinusoidal wave alternating-current voltage
that varies in a range of .+-.3.0 V is applied at 1 kHz. The
respective signal waveforms as the drive signals of the first
circulating elements 16 and 16' and the second circulating elements
17 and 17' according to the present embodiment are not limited to
those described previously. It is possible to selectively set the
voltage, the frequency, and the drive waveform in a range in which
desired flow velocity is obtained for the liquid flow path
circulatory flow 18 and the liquid chamber circulatory flow 19
described previously.
As shown in FIG. 5B, the driving timing of the first circulating
elements 16 and 16' and the second circulating elements 17 and 17'
is not interlocked with the driving timing of the energy generating
element 11. In the ejection standby state, by both the first
circulating element 16 and the second circulating elements 17 and
17' driving at all times, the liquid flow path circulatory flow 18
and the liquid chamber circulatory flow 19 are formed.
About Effect of the Present Embodiment
By the above configuration, an ink flow that advances from one end
toward the other within the liquid flow path 13 occurs by the first
circulating elements 16 and 16' and a fresh ink flow that crosses
the liquid chamber 21 occurs. Further, by the second circulating
elements 17 and 17', an ink flow component that advances toward the
ejection port 12 within the liquid chamber 21 occurs. By the
configuration such as this, which combines the first circulating
element and the second circulating element, by pushing out the
thickened ink within the ejection port 12 into the liquid chamber
21 and sending fresh ink into the liquid chamber 21, it is made
possible to efficiently discharge the concentrated ink to the
outside of the liquid chamber 21. Consequently, according to the
present embodiment, it is possible to eject comparatively fresh ink
whose effect of mitigating ink thickening within the ejection port
12 is significant and whose degree of thickening is low. Further,
in the present embodiment, by adopting the configuration that does
not use a heating element for formation of the liquid flow path
circulatory flow 18, it is made possible to suppress a rise in
temperature of the liquid ejection head to a degree lower than that
in the first embodiment. As a result, it is made possible to reduce
image color unevenness.
Third Embodiment
In the following, a printing element substrate of a liquid ejection
head according to a third embodiment of the present invention is
explained. In the following explanation, differences from the first
embodiment are explained mainly. The contents of the portion whose
specific explanation is omitted are the same as those of the first
embodiment.
FIG. 7A is a schematic diagram showing the structure of the
printing element substrate 1 of the liquid ejection head according
to the third embodiment of the present invention. Specifically,
FIG. 7A is a diagram showing a plane obtained by truncating the
printing element substrate 1 in a plane parallel to the bonding
face of the support substrate 10 and the ejection port forming
member 15. FIG. 7B is a schematic diagram showing a liquid movement
direction and a flow velocity distribution on a section along a
VIIB-VIIB line in FIG. 7A.
As shown in FIG. 7A, in the present embodiment, the liquid flow
path 13 for each ejection port 12 changes its direction by
180.degree. on the way and is connected to the same liquid supply
flow path 14 at both ends of the flow path. That is, the
configuration is such that the ink supplied from the liquid supply
flow path 14 returns to the liquid supply flow path 14 again via
the liquid flow path 13 and the liquid chamber 21. In a case where
the configuration such as this is adopted, it is not necessary to
arrange the two liquid supply flow paths for one ejection port,
which is necessary in the first embodiment (see FIG. 1B).
Consequently, in the present embodiment, it is easy to reduce the
dimension in the width direction of the support substrate 10
compared to the first embodiment and it is possible to downsize the
printing element substrate 1.
In the present embodiment, the first circulating element 16 is a
heating element. Symbol 110 in FIG. 4C indicates a pulse wave as
the drive signal of the first circulating element 16. As shown in
FIG. 4C, in order to drive the first circulating element 16, a
voltage of 24 V is applied at 1 kHz. As a result of that, the
liquid flow path circulatory flow 18 that advances from one end
toward the other end of the liquid flow path 13 occurs as shown in
FIG. 7A and FIG. 7B.
The second circulating elements 17 and 17' are configured by two
electrodes. In the present embodiment, as shown in FIG. 7A, the
second circulating elements 17 and 17' are arranged on both sides
of the energy generating element 11 within the liquid chamber 21 so
that the second circulating elements 17 and 17' are arranged side
by side in the flow direction of the liquid flow path 13. The
arrangement position of the second circulating element is not
limited to this and it is possible to arrange the second
circulating element at an arbitrary position within the liquid
chamber 21.
As shown in FIG. 4C, in order to drive the second circulating
elements 17 and 17', a sinusoidal wave alternating-current voltage
that varies in a range of .+-.15 V is applied at 1 MHz. As a result
of that, as shown in FIG. 7B, a flow velocity distribution occurs
within the liquid chamber 21, in which the flow velocity is high at
the surface of the support substrate 10 and the flow velocity
approaches zero as the ejection port forming member 15 becomes
nearer, resulting in formation of the liquid chamber circulatory
flow 19. The reason this flow velocity distribution occurs is
explained by using FIG. 8A to FIG. 8C.
The two electrodes configuring the second circulating elements 17
and 17' are taken to be the first electrode 310 and the second
electrode 311. The first electrode 310 and the second electrode 311
have the same dimension. In the present embodiment, the frequency
of the drive signal to be applied to these electrodes is about 100
kHz to 100 MHz and a high-frequency alternating-current voltage is
applied. In a case where an alternating-current voltage is applied
between thin film electrodes, a temperature distribution as shown
in 8A is formed in the solution due to the Joule heat. Charges
induced by the electric field that is applied migrate and a flow as
indicated by an arrow in FIG. 8B occurs. This flow is called an AC
electrothermal flow (ACETF).
The AC electrothermal flow is a flow phenomenon that is elicited
mainly under the conditions of a high frequency (specifically, 100
kHz or higher) and a high conductivity (specifically, 0.1 Sm.sup.-1
or higher) and forms a circulatory flow as indicated by an arrow in
FIG. 8C. While the electroosmotic flow is characterized by that a
strong liquid flow is obtained by ink whose electric conductivity
is low, the AC electrothermal flow is characterized by that a
strong liquid flow is obtained by ink whose electric conductivity
is high. Further, the specifications of the power source necessary
at the time of drive are also different, and therefore, it is
possible to arbitrarily select elements used for the first
circulating element 16 and the second circulating element 17 in
accordance with the circulation flow velocity, the ink type, the
configuration of the printing element, and the like.
By the electrothermal current such as this, which is a steady flow,
a flow velocity distribution occurs (see FIG. 7B), which forms two
vortexes at positions substantially symmetrical with respect to the
energy generating element 11 or the ejection port 12 as a
reference. A flow component that passes the vicinity of the
ejection port 12 is formed. and therefore, it is possible to cause
the ink concentrated in the vicinity of the ejection port 12 to
flow. Consequently, it is easy to suppress ink concentration in the
vicinity of the ejection port 12. The second circulating elements
17 and 17' are connected to the alternating-current power source AC
and a drive voltage whose frequency is high compared to that of the
first embodiment is applied, and therefore, the occurrence of
bubbles by water electrolysis is suppressed and it is made possible
to make the drive voltage higher than that in the first
embodiment.
As shown in FIG. 5C, the driving timing of the first circulating
element 16 and the second circulating elements 17 and 17' is
interlocked respectively with the driving timing of the energy
generating element 11. Specifically, the first circulating element
16 drives by avoiding the period during which the energy generating
element 11 is driving and a predetermined period before and after
the drive thereof so that the first circulating element 16 is not
affected by bubble generation by the energy generating element 11,
which is a heating element, and the pressure variation by ink
refill, and thus, the liquid flow path circulatory flow 18 is
formed. Then, in order to reduce the influence of heating due to
bubble generation, drive and non-drive are repeated periodically.
Further, in order to suppress the influence on ejection due to the
circulatory flow within the liquid chamber 21, the second
circulating elements 17 and 17' also drive by avoiding the period
during which the energy generating element 11 is driving and a
predetermined period before and after the drive thereof. It is
preferable for the driving frequency (number of driving times per
unit time) of the first circulating element to be lower than the
driving frequency of the second circulating frequency. However, the
drive conditions of the present embodiment are merely exemplary and
the voltage, the frequency, the waveform of the drive signal, and
the driving timing are not limited.
About Effect of the Present Embodiment>
In the present embodiment, also in a case where ink is not being
ejected, a flow is formed in which the ink having flowed into the
liquid flow path 13 from the liquid supply flow path 14 returns
again to the liquid supply flow path 14. Further, it is possible to
drive the second circulating elements 17 and 17' under the
condition of a voltage higher than that of the first embodiment,
and therefore, it is made possible to form a within-liquid chamber
circulatory flow stronger than that of the first embodiment.
Because of this, like the first embodiment, the effect of
suppressing stagnation of concentrated ink within the liquid
chamber 21 is obtained.
Fourth Embodiment
In the following, a printing element substrate of a liquid ejection
head according to a fourth embodiment of the present invention is
explained. In the following explanation, differences from the first
embodiment are explained mainly. The contents of the portion whose
specific explanation is omitted are the same as those of the first
embodiment.
FIG. 9A is a schematic diagram showing the structure of the
printing element substrate 1 of the liquid ejection head according
to the fourth embodiment of the present invention and specifically,
FIG. 9A is a diagram showing a plane obtained by truncating the
printing element substrate 1 in a plane parallel to the bonding
face of the support substrate 10 and the ejection port forming
member 15. FIG. 9B is a schematic diagram showing a liquid movement
direction and a flow velocity distribution on a section along an
IXB-IXB line in FIG. 9A. FIG. 9C is an enlarged diagram of a
one-dot chain line area IXC in FIG. 9B.
In the support substrate 10, a plurality of through holes 24 and a
plurality of through holes 24' are formed, both penetrating from
the surface of the support substrate 10 to the backside. As shown
in FIG. 9A, the liquid chamber 21 and the through holes 24 and 24'
are provided for each corresponding ejection port 12. With the
ejection port row configured by a plurality of the ejection ports
12 being sandwiched in between, a first through hole row configured
by the plurality of the through holes 24 and a second through hole
row configured by the plurality of the through holes 24' extend in
parallel. Although not shown in FIG. 9B, on the lower side of the
support substrate 10, a liquid supply flow path that communicates
with both the through holes 24 and the through holes 24' is
provided in FIG. 9B and this liquid supply flow path is shared by
the through holes 24 and the through holes 24'.
In the present embodiment, the first circulating element 16 is a
heating element and formed in the support substrate 10. Further,
the second circulating elements 17 and 17' are electrothermal flow
elements and formed on the surface on the side of the liquid flow
path 13 of the ejection port forming member 15. By the
configuration of the present embodiment, as shown in FIG. 9B, it is
possible to arrange the second circulating elements 17 and 17' in
the vicinity of the ejection port 12 (in the vertical direction in
FIG. 9B) compared to the embodiments described previously. Further,
as shown in FIG. 9A, it is made possible to arrange the second
circulating elements 17 and 17' so as to overlap the energy
generating element 11 within the plane of the support substrate 10.
Consequently, it is also made possible to arrange the second
circulating elements 17 and 17' in the closer vicinity of the
ejection port 12 (in the horizontal direction in FIG. 9A) compared
to the embodiments described previously. Consequently, in the
vicinity of the ejection port 12, it is possible to form the liquid
chamber circulatory flow 19 as a strong vortex flow that advances
from the ejection port forming member 15 toward the support
substrate 10. Accompanying the formation of the vortex flow, an
involving flow 25 occurs, and therefore, it is possible to replace
the ink within the ejection port 12 more efficiently.
About Effect of the Present Embodiment
In the present embodiment, also in a case where ink is not being
ejected, a flow is formed in which the ink having flowed into the
liquid flow path 13 from the through hole 24 flows to the outside
of the liquid flow path 13 from the through hole 24'. Further, by
the second circulating elements 17 and 17' arranged in the vicinity
of the ejection port 12, it is made possible to form the liquid
chamber circulatory flow 19 more effective than that of the
embodiments described previously (see FIG. 1D and the like), and
therefore, it is possible to efficiently replace the concentrated
ink within the ejection port 12. Because of this, like the first
embodiment, the effect of suppressing stagnation of concentrated
ink within the liquid chamber 21 is obtained.
Fifth Embodiment
In the following, a printing element substrate of a liquid ejection
head according to a fifth embodiment of the present invention is
explained. In the following explanation, differences from the first
embodiment are explained mainly. The contents of the portion whose
specific explanation is omitted are the same as those of the first
embodiment.
FIG. 10A is a schematic diagram showing the structure of the
printing element substrate 1 of the liquid ejection head according
to the fifth embodiment of the present invention and specifically,
FIG. 10A is a diagram showing a plane obtained by truncating the
printing element substrate 1 in a plane parallel to the bonding
face of the support substrate 10 and the ejection port forming
member 15. FIG. 10B is a schematic diagram showing a liquid
movement direction and a flow velocity distribution on a section
along an XB-XB line in FIG. 10A. FIG. 10C is an enlarged diagram of
a one-dot chain line area XC in FIG. 10B.
In the fourth embodiment described previously, the through holes 24
and 24' for each ejection port 12 are provided (see FIG. 9A). In
contrast to this, in the present embodiment as shown in FIG. 10A, a
pair of the through holes 24 and 24' is shared by a plurality of
the (for example, three) ejection ports 12. With an ejection port
row configured by a plurality of the ejection ports 12 being
sandwiched in between, a first through hole row configured by a
plurality of the through holes 24 and a second through hole row
configured by a plurality of the through holes 24' extend in
parallel, and this is the same as in the fourth embodiment.
By adopting the configuration such as this, it is possible to
substantially increase the dimension of the through holes 24 and
24' in the direction parallel to the extension direction of the
ejection port row 20 compared to the fourth embodiment.
Consequently, it is possible to reduce the dimension of the through
holes 24 and 24' in the direction perpendicular to the extension
direction of the ejection port row 20 by an amount corresponding
thereto compared to the fourth embodiment. Because of this,
compared to the third embodiment, it is easy to reduce the
dimension in the width direction of the printing element substrate
1, and therefore, it is possible to downsize the printing element
substrate 1. It may also be possible to provide one of the two
through holes for each liquid flow path 13 as in the third
embodiment.
In the present embodiment, the first circulating elements 16 and
16' are electrothermal flow elements in which an asymmetrical
electrode pair is arranged and formed on the support substrate 10
as shown in FIG. 10B. By making the first circulating elements 16
and 16' an electrode pair whose lengths in the flow path direction
are asymmetrical, an electric field asymmetrical in the flow path
direction is formed and a liquid flow that advances in one
direction from the electrode whose electrode length is short toward
the electrode whose electrode length is long occurs. Further, the
second circulating elements 17 and 17' are electrothermal flow
elements and formed on the sidewall surface on the side of the
ejection port 12 in the ejection port forming member 15 as shown in
FIG. 10C. By laying out the configuration such as this, it is
possible to arrange the second circulating elements 17 and 17'
inside the ejection port 12. Consequently, it is possible to form a
flow distribution that replaces the ink within the ejection port 12
more efficiently than the embodiments described previously. Here,
the case is described where as for the electrode pair of the second
circulating elements 17 and 17', the entire electrodes are arranged
inside the ejection port 12, but what is required is that at least
a part of the electrode be arranged inside the ejection port
12.
About Effect of the Present Embodiment
In the present embodiment, also in a case where ink is not being
ejected, a flow is formed in which the ink having flowed into the
liquid flow path 13 from the through hole 24 flows out to the
outside of the liquid flow path 13 from the through hole 24'.
Further, by the second circulating elements 17 and 17' arranged
within the ejection port 12, it is made possible to form the liquid
chamber circulatory flow 19 more effective than that of the
embodiments described previously (see FIG. 1D and the like), and
therefore, it is possible to efficiently replace the concentrated
ink within the ejection port. Because of this, like the first
embodiment, the effect of suppressing stagnation of concentrated
ink within the liquid chamber 21 is obtained.
Sixth Embodiment
By using FIG. 11A and FIG. 11B, the configuration of a printing
element substrate of a liquid ejection head according to a sixth
embodiment of the present invention is explained. In the following
explanation, differences from the first embodiment are explained
mainly, and therefore, the contents of the portion whose specific
explanation is omitted are the same as those of the first
embodiment.
FIG. 11A and FIG. 11B are each a schematic diagram showing the
structure of the printing element substrate 1 of the liquid
ejection head according to the sixth embodiment of the present
invention and specifically, FIG. 11A is a diagram showing a plane
obtained by truncating the printing element substrate 1 in a plane
parallel to the bonding face of the support substrate 10 and the
ejection port forming member 15. FIG. 11B is a schematic diagram
showing a liquid movement direction on a section along an XIB-XIB
line in FIG. 11A.
As shown in FIG. 11A, in the present embodiment, the liquid flow
path 13 for each ejection port 12 changes its direction by
180.degree. on the way and is connected to the same liquid supply
flow path 14 at both ends of the flow path. In the liquid supply
flow path 14, the through hole 24 extending across a plurality of
the liquid flow paths 13 is formed. As described above, the through
hole 24 has a great width in the extension direction compared to
the direction perpendicular to the extension direction of the
ejection port row 20.
In the present embodiment, the first circulating element 16 is a
heating element arranged in the support substrate 10. Compared to
the third embodiment (see FIG. 7A) in which the size of the first
circulating element 16 and the size of the energy generating
element 11 are substantially the same, the area of the portion of
the first circulating element 16 according to the present
embodiment, which comes into contact with ink, is large, and
therefore, it is possible to cause the liquid flow path circulatory
flow 18 to occur more strongly. The second circulating elements 17
and 17' are electroosmotic flow elements and formed on the support
substrate 10 and within the liquid chamber 21 in a form sandwiching
the energy generating element 11 in between.
About Effect of the Present Embodiment
In the present embodiment, by adopting the first circulating
element 16 larger than that of the embodiments described
previously, also in a case where ink is not being ejected, a flow
is formed more strongly in which the ink having flowed into the
liquid flow path 13 from the through hole 24 flows out to the
outside of the liquid flow path 13 from the through hole 24.
Further, by the second circulating elements 17 and 17' arranged
within the liquid chamber 21, it is possible to replace
concentrated ink within the ejection port 12. Because of this, like
the first embodiment, the effect of suppressing stagnation of
concentrated ink within the ejection port 12 and within the liquid
chamber 21 is obtained.
Other Embodiments
Embodiment(s) of the present invention can also be realized by a
computer of a system or apparatus that reads out and executes
computer executable instructions (e.g., one or more programs)
recorded on a storage medium (which may also be referred to more
fully as a `non-transitory computer-readable storage medium`) to
perform the functions of one or more of the above-described
embodiment(s) and/or that includes one or more circuits (e.g.,
application specific integrated circuit (ASIC)) for performing the
functions of one or more of the above-described embodiment(s), and
by a method performed by the computer of the system or apparatus
by, for example, reading out and executing the computer executable
instructions from the storage medium to perform the functions of
one or more of the above-described embodiment(s) and/or controlling
the one or more circuits to perform the functions of one or more of
the above-described embodiment(s). The computer may comprise one or
more processors (e.g., central processing unit (CPU), micro
processing unit (MPU)) and may include a network of separate
computers or separate processors to read out and execute the
computer executable instructions. The computer executable
instructions may be provided to the computer, for example, from a
network or the storage medium. The storage medium may include, for
example, one or more of a hard disk, a random-access memory (RAM),
a read only memory (ROM), a storage of distributed computing
systems, an optical disk (such as a compact disc (CD), digital
versatile disc (DVD), or Blu-ray Disc (BD).TM.), a flash memory
device, a memory card, and the like.
According to the present invention, thickening of a liquid due to
evaporation from an ejection port is mitigated and it is made
possible to stably eject the liquid from the ejection port.
While the present invention has been described with reference to
exemplary embodiments, it is to be understood that the invention is
not limited to the disclosed exemplary embodiments. The scope of
the following claims is to be accorded the broadest interpretation
so as to encompass all such modifications and equivalent structures
and functions.
This application claims the benefit of Japanese Patent Application
No. 2018-241290, filed Dec. 25, 2018, which is hereby incorporated
by reference herein in its entirety.
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